Sideseam joint for a carton

ABSTRACT

According to the practice of this invention, the noted unwanted adhesion between the second panel and the first panel attendant the formation of the sideseam joint is eliminated by providing the second panel with a cutout. That portion which is cut out corresponds in form to the triangular cutout or truncated portion at the tapered end of the sideseam forming fifth panel. In this way, when compression of the first panel against the sideseam panel and the first panel occurs, there is no hot and sticky exposed area of the first panel which will adhere to the second panel.

BACKGROUND OF THE INVENTION

[0001] This invention relates to paperboard containers of the type often used for the packaging of liquids such as milk and fruit juices. Such containers are fashioned from a unitary blank of paperboard, usually coated on both its interior and exterior forming surfaces with one or more barrier layer materials, cut and scored, erected and filled on automatic machinery to form gable top liquid packages. Such containers have a flat bottom and a gable top upper or roof section, the latter being adapted to form a pour spout when opened, all as known. An intermediate step in making such containers is the formation of a tube structure from the blank, with the steps of forming the end closures and filling with liquid taking place after tube formation.

[0002] In the formation of a gable top containers from a unitary blank having a plurality of wall forming panels serially arranged, one step involves forming a tube by folding the blank so that the fifth or sideseam forming panel is superposed over an edge zone of the free edge portion of the first sidewall forming panel. A part of the carton interior forming surface of the first panel has been heated so as to partially melt the usual polyethylene coating and make the latter sticky. Similarly, that portion of the fifth or sideseam panel which is to be in surface contact with the first panel free edge zone has also been heated so as to make its polyethylene coating sticky. The transverse cross sectional configuration of the now folded blank is substantially that of a shallow diamond, with a force applied to the upper two panels collapsing the diamond shaped tube, resulting in a force applied to the sideseam flap or panel to seal it to the edge zone portion of the first panel.

[0003] Often, the sideseam is skived, with the particular skiving process/apparatus employed unavoidably resulting in a taper at one end of the sideseam forming or fifth panel, at the bottom carton closure. This taper causes a partial triangular uncovering of the first panel edge zone, so that when the first and fourth panels are pushed downwardly to compress and seal the sideseam (fifth) panel against an edge zone of the second panel, a portion of the second panel will contact an exposed hot and sticky triangular portion of the first panel and cause an unwanted adhesion between a triangular portion of the first panel, near the tapered end of the sideseam panel, and the triangular portion of the second panel. In order to avoid this unwanted adhesion, the temperature of the heated first panel edge portion and the temperature of the fifth or sideseam forming panel was reduced to reduce the stickiness. While solving the problem of unwanted adhesion, such temperature reduction diminished the strength and quality of the seal between the sideseam panel and the first panel. This lowered quality becomes unacceptable with extended shelf life liquid cartons.

SUMMARY OF THE INVENTION

[0004] According to the practice of this invention, the noted unwanted adhesion between the second panel and the first panel attendant the formation of the sideseam joint is eliminated by providing the second panel with a cutout. That portion which is cut out corresponds in form to the triangular cutout or truncated portion at the tapered end of the sideseam forming fifth panel. In this way, when compression of the first panel against the sideseam panel and the first panel occurs, there is no hot and sticky exposed area of the first panel which will adhere to the second panel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIG. 1 is a plan view of a prior unitary paperboard blank for forming a gable top liquid carton.

[0006]FIG. 2 is a partial perspective view illustrating a typical prior art step in the formation of a seamed tube from a unitary bank cut and scored for producing a gable top container, and illustrates how unwanted adhesion occurs. For purposes of illustration and explanation, the second and third sidewall panels are shown in a position above the first and fourth sidewall panels. In practice, these relative positions are reversed, with panels 16 and 14 nearly coplanar.

[0007]FIG. 3 is a plan view of a unitary blank of paperboard provided with the cutout in the first panel.

[0008]FIG. 4 is a view similar to FIG. 2, but with the blank of FIG. 3.

[0009]FIG. 5 is a plan view of a unitary blank of paperboard provided with a cutout in the second panel.

[0010]FIG. 6 is a view similar to FIG. 2, but with the blank of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

[0011] Referring now to FIG. 1, a unitary paperboard 10 includes first, second, third, and fourth sidewall forming panels and a fifth, sideseam forming panel. These panels are denoted as 12, 14, 16, 18, and 20 respectively. The upper ends form a gable top when folded and erected, while the lower ends of the panels form a bottom closure. Tab 24 is conventional, and taper 28 is formed during the left or free edge skiving of fifth or sideseam forming panel 20. An imaginary triangular zone, later to be described, is bounded by imaginary lines 32 and 34. Right edge zone 40 of first panel 12 denotes a sealing area, later to be described. Both surfaces of the blank are provided with barrier layer coatings, including polyethylene, as is convectional. FIG. 2 illustrates a step in the formation of a tube from paperboard blank 10 for forming a gable top container. The paperboard blank is folded to form a tube having a longitudinal axis (the latter not shown) with sideseam panel 20 placed so as to overlap a part or zone 40 of the free edge of panel 12. Prior to this, the lower surface (as viewed at FIG. 2) of sideseam forming panel 20 has been heated, as by flame or other treatment, as has been that portion of panel 12 (see area 40 of FIG. 2) which will be in surface contact with sideseam panel 20. These two heated surfaces are at a higher temperature (not necessarily the same) than their respective surfaces on opposite sides of the blank. Second panel 14 and third panel 16 are now pressed downwardly, so that panel 14 presses the heated surface of sideseam forming panel 20 against the locally heated edge portion 40 of first panel 12. The thermoplastic on these portions of panels 20 and 12, because they have been heated, becomes tacky, with result that a joint or seam is formed between panels 12 and 18.

[0012] By virtue of taper 28 on sideseam forming panel 20, a triangular zone 30 is formed which is also heated with the rest of the free edge portion of panel 12. Accordingly, when panels 14 and 16 are pushed downwardly to apply pressure to form the sideseam joint or seam between panels 12 and 20, a corresponding portion 30A of second panel 14 becomes adhered to the hot and sticky triangular portion 30 of panel 12. This adhesion renders the tube unusable for further processing into a gable top carton. In the past, only lowering the surface thermoplastic (typically polyethylene) softening temperature of panels 12 and 20 eliminated the problem, but at the cost of an inferior sideseam joint.

[0013] Referring now to FIG. 3, the blank of U.S. Pat. No. 5,626,285 is shown and differs from the blank of FIG. 1 only in the removal of a triangular zone bordered by cut lines 34 and 36.

[0014] Referring now to FIG. 4, it is seen that when panels 14 and 16 are pressed downwardly to form the sideseam joint, there will be no zone or portion of panel 12 beyond taper 28 which will stick to panel 14 at region 30A. Thus, what is shown at FIG. 4 is conventional, except for cut lines 34 and 36 and the consequent absence of triangular zone 30 of FIG. 2. The cutout shown at FIGS. 3 and 4 is bordered by lines 34 and 36 and is triangular. FIG. 4 shows edges 28 and 34 as coincident. If desired however, cut line 36 could be curved or could extend straight downwardly, parallel to zone 40, instead of at an angle as shown at FIG. 3. As earlier stated, in practice the seam forming step shown at FIGS. 2 and 4 is carried out with the tube formed from the sidewalls and the fifth panel 20 rotated 180 degrees about its longitudinal axis.

[0015] When the carton described in U.S. Pat. No. 5,626,285 is utilized in small sized cartons, a difficulty has been encountered in forming the bottom of the carton prior to filling with automated machinery. The notch in the first panel has a tendency to prevent the clean folding of the gable tips formed in the second and fourth panels. It is therefore advantageous to move the cutout from the first panel to the second panel but still in a position that corresponds to the exposed glue formed by the truncation of the glue flap.

[0016] Referring now to FIG. 5, the blank of the invention is seen. The second panel 14 has a notch made from free edges 134, 136. Edge 136 corresponds to a line 34 demarcating the truncated edge of the glue flap 20 after it is joined to the first panel 12 to form the a tubular carton. The free edge 134 extends from the edge 136 to the bottom of the third panel 16.

[0017]FIG. 6 depicts when the tube is flattened how the notch overlies the exposed glue area 30 created as the glue flap 20 overlies the glue area 40 of first panel 12. The free edge 136 of the notch corresponds to the truncated edge of the glue flap 20 so that the exposed adhesive area 32 does not come in contact with the portion of the second panel of the carton 14. In this way, unwanted adhesion of the flattened tube is prevented. When flattened, the first and fourth panels 12, 18 form a lower layer and second and third panels 14 and 16 form the upper layer. The upper layer does not have a portion that may become adhered to the lower layer. The carton is shipped in this configuration until its ultimate formation into a carton filled and sealed.

[0018] While the invention has been described in the preferred embodiment, modifications and variations would be obvious to one of ordinary skill in the art without departing from the spirit of the invention. The description is not intended to be eliminating in any way, but is defined by the appended claims. 

What is claimed is:
 1. A paperboard blank for forming a container, comprising: a first, second, third, fourth and fifth panel serially connected along fold lines, said fifth panel adapted to overlap said first panel to form a carton sideseam, said fifth panel truncated at one end, and a cut out in one end of said second panel.
 2. The paperboard blank of claim 1, wherein said cut out has a shape corresponding to the shape of the fifth panel truncation.
 3. The paperboard blank of claim 1, wherein said cut out is triangular.
 4. The paperboard blank of claim 1, wherein said cut out extends into said third panel.
 5. A tubular structure for forming a container, comprising: a first, second, third, fourth and fifth panel serially connected along fold lines, said fifth panel overlapping said first panel to form a carton sideseam, said fifth panel truncated at one end, and a cut out in one end of said second panel.
 6. The tubular structure of claim 5, wherein said cut out has a shape corresponding to the shape of the fifth panel truncation.
 7. The tubular structure of claim 5, wherein said cut out is triangular.
 8. The tubular structure of claim 5, wherein said cut out extends into said third panel. 